EMG Flashcards
What is EMG?
electromyogram
current fields
AP
What can be measured with the EMG electrode?
filtered MUAPT(s)
summation of output (electrical activity) from multiple fibers
or single MUAPT
What does it mean by interference EMG?
sum of many MUAPs
How is the sEMG decoded to extract insights into muscle activity?
preprocessing
decomposition e.g. BSS
feature extraction e.g. RMS, STA
analysis e.g. temporal/spatial
How can HD-EMG be decomposed?
separation of sources (MUs) via BSS: EMG –> MU impulse trains
algorithm: Independent Component Analysis
visual inspection
raster plot of identified MUs
What is the Convolutive Mixture model? Why and how is it used in sEMG recordings?
represent sEMG signal
as sum of convolutions between MU spike trains and their corresponding APs, plus additive noise
MN discharge =>spike trains
MUAPT=>AP trains of MUs
+ noise e.g. system, filter
Why is the firing train crucial in using a convolution mixture model, particularly for intervention in patient movement?
temporal dynamics of movement
What are the separation vectors in the context of Independent Component Analysis (ICA) applied to sEMG signals?
represent the weights or coefficients that define how much each source (estimated MUAP) contributes to the observed signal x (sEMG)
use ICA to find those vectors
vectors build separation matrix W
W* x = s
s: MU spike trains
What is RMS? How can it be used for movement investigation?
root-mean-square values of varying signal –> square root of the average power of the signal
quantify the overall magnitude
–> assess the overall activity level of muscles over time
e.g. before decomposition
What would be the effect of a longer time window length on the RMS values?
amplitude changes in RMS values
short –> higher variability
long –> consistent amplitude, smooth, emphasize the overall signal trend
What is the basic idea of wearable MyoNeuro interface?
neural interfaces: HD-sEMG –> possible integrated into the fabric of form-fitting garments –> wearable sensing interface
detecting features of the EMG activity that are linked robustly to motor intent –> control robotic or prosthetic devices
What is TMR?
Targeted Muscle Reinnervation (TMR) surgery
enables the control of a myoelectric prosthesis using redirected nerves
What are the pros and cons of sEMG and iEMG?
sEMG: + more surface, non-invasive possible - noisier - need surface amplifier
iEMG: + more localized signal, selective, clear AP - narrow selective area, weak signal
What are some sEMG preprocessing steps?
Filtering
Rectification
Smoothing
Normalization
Anomaly Correction
What are the chosen ranges of noise to be considered for filtering EMG?
EMG: 40-600 Hz
Ambient noise: 1Hz - several kHz
Powerline Interference 50-60Hz
